Microwave modulator and switch



Sept. 29. 1959 F. REGGIA UAL 2,906,974

MICROWAVE MonuLAToR AND swITcH Filed Aug. 24, 1956 -Modulunq SignalInpui ,IIIlII/IIA Frank Reggia lyoy Conway LeCraw yttorngys ...cc-Y

United States Patei't lee of jnerewaveenergyynew.""lvlljmfeg1p'articnl'arnf-, the invennen provides nuegewaveyswitching arrangement-fs" in 2,906,974 Patented. .Serb 29 1959 eresistor "z3," 'iev'nfg switch '24 ues'eaj if ne eier-ent through coil 20 risrof the correct 'n'` he effec- 2,906,974 A i TBetkesa-Md-,ssiguqrstuthelluited States, offAmerica as represented bythe Secretary of the Army y Appiieuon August 24, -19s6-,fs`'ri No."ses-,152

relatie. (Crass-98) (Granted under YTitle 35, USS. Code (1952), sec.266) The invention described kherein maybe manufactured and used byorforh'rGovernrerit'for governmental purposes i epayrnleiit' to usoflaliyro'yaliy thereon.

This invention relates to yiihe"'control of the amplitude Y Igpiesefnuyvravailabieteintes,lilas larab, wijle rheswitch is "une: urgewhich ythe"lieu/"of microwav'eeiiergy-o'f a "frequency fo through awaveguide section may be controlled by the application of a magnetic eldto a ferrite body within waveguide 12 that is observed when current isapplied the section; application of the magnetic field so affects tocoil may be explained by the following theory. The the effectivepermeability of the ferrite as to change the fo linearly polarizedenergy entering the input end of effective cut-off frequency of thesection from a value waveguide 12 may be considered to be the resultantof above fo to a value below fo, thereby permitting energy twocircularly-polarized waves of equal amplitude, one ow to the output endof the section. negative and the other positive. With no applied mag- Anobject of the invention is to provide a device for netic field theeffective permeability of the ferrite 18 controlling the amplitude ofmicrowave energy flow that for both these waves is identical-typically,approxiaffords a wide range of attenuations, requires little energymately 0.8. When a longitudinal magnetic field is apfor actuation, andis substantially non-dissipative, fastplied, however, the effectivepermeability of the ferrite acting, reliable, durable, and readilyfabricated at low increases to approximately 1.7 for the negative wave,decost. creasing at the same time to approximately zero for the Otherobjects, aspects, uses and advantages of the inpositive wave. Theeffective electrical diameter of wavevention will become apparent fromthe following deguide 12 for the negative wave is thus increasedsuffiscription and the accompanying drawings, in which: ciently topermit propagation of the wave. Because of Fig. 1 is a simplifiedlongitudinal sectional and schethe low insertion loss obtained, webelieve that a conmatic representation :of a form. of microwave switchin version process occurs at the input and output of the accordance withthe invention. switch whereby an 4appreciable percentage of the positiveFig. 2 is a simplified longitudinal section and schematic wave energy isconverted to negative wave energy, and representation of another switchin accordance with the hence propagates. invention, mounted between twosections of flanged Wave- Fig. 2 shows an arrangment for convenientlymountguide. ing a switch in accordance with the invention between InFig. 1 a circular waveguide section 12 is shown intwo conventionalpieces of rectangular waveguide 32 tegral with an input waveguidesection 14 and an out- 45 and 34 having anges 36. putwaveguide section16. A coaxial ferrite rod 18 In Fig. 2 a switch subassembly 40 includes:a main is positioned within waveguide 12. A solenoid 20 is metallicplate 42, the length and width of which preferwound around waveguide 12.A battery 22 is connectably correspond to the outer dimensions offlanges 36; a able through a resistor 23 to solenoid 20 by means ofmetallic ground plate 44 the length and width of which a single-polesingle-throw switch 24. are slightly less than the internalcross-sectional dimen- With switch 24 open, waveguide 12 has a certaincutsions of waveguides 32 and 34, plate 44 being parallel to oiffrequency fel-Le., little or no energy of frequencies plate 42; a lengthof circular waveguide 46 having its less than fel will propagate throughwaveguide 12. Let axis perpendicular to plates 42 and 44 and extendingbea microwave input signal of frequency fo, slightly less tween plates42 and 44; a ferrite rod 48 extending cothan fel, be applied to inputwaveguide 14. With switch axially throughwaveguide 46 and through plates42 and 24 open, little or none of the fo signal will reach output 44; asolenoid 50 wound coaxially around waveguide 46; waveguide 16. Now letswitch 24 be closed. The rea wire lead 52 electrically grounding one endof solenoid sulting ow of current through solenoid 20 causes a 50 tomain plate 42; and another wire lead S4 extendmagnetic field to beapplied to ferrite 18 and lowers ing insulatedly from the other end ofsolenoid 50, through the eifective cut-olf frequency of waveguide 12 toa new 60 a passageway 5S in main plate 42, to a point beyond value fegthat is lower than fel and that may be made the outer edge of plate 42.lower than fo. The fo energy in waveguide 14 thus be- Subassembly 40 isreadily mounted by sandwiching comes coupled through waveguide 12 tooutput wavemain plate 42 between flanges 36 of waveguides 32 and guide16. It will be understood that the fo output from 34. The completeassembly may be held together by waveguide 16 may be switched on and olfat very high 65 any usual or convenient means such as the screws 56rates by switching on and olf the current applied to soleshown. noid 20.Various devices can be coupled to, or substi- From what has been said inconnection with Fig. 1, tuted for, waveguide 16. Or waveguide 16 may beit will be understood that the coupling of microwave omitted; energywill then Ibe radiated from the output energy from waveguide 32 towaveguide 34 can be conend of rod 1S. 70 trolled, within a certainfrequency range, by supplying If desired, a modulating signal may beapplied across current to solenoid 50 by means of wire lead 54. i

g We believe that the lowering of cut-off frequency of It will beapparent that the embodiments shown are only exemplary andv that variousrnodiications can be made in construction and arrangement within thescope of the invention as defined in the appended claim.

We claim:

A -microwave switch for mounting between two sections of standard angedrectangular waveguide and adapted for use at a frequency fo, comprising:a rectangular main metallic plate adapted to be mounted between theflanges of said two sections; a rectangular metallic ground plateparallel to said main plate and of lesser length and width than theinterior dimensions of said lsections so as to be disposable therein; alength of reduced circular waveguide having its axis perpendicular toboth of said plates and extending between said plates; a ferrite rodextending coaxially through said circular waveguide and throughapertures in said plates and substantially lilling said waveguide; acoaxial solenoid around said circular waveguide; and means for applyingan electrical current to said solenoid; the dimensions of the elementsbeing selected so that the cut-off frequency of said reduced circularwaveguide section with said ferrite rod extending therethrough isslightly higher than fo when no current is `applied to said solenoid,said means for applying an electrical current being adapted so that theapplication of current to the solenoid causes said cut-oil? frequency tofall below fo and thus permit the ow of fo energy between said twosections of rectangular waveguide.

References Cited in the tile of this patent UNITED STATES PATENTS OTHERREFERENCES Van Trier: Applied Scientilic Research, sec. B, vol. 3, No.2, July 1953, pages 142-144.

Fox et al.: Behavior and Applications of Ferrites in the MicrowaveRegion, The Bell System Technical J ournal,V vol. 34, No. 1, January1955, pages 5-103.

